As this type of lamp unit, a lamp unit is known which includes a part called a rotary shade. The rotary shade is a part which has a turning axis which extends in a left-to-right direction of the vehicle, and a plurality of light blocking plates having different edge shapes are provided on the turning axis in different angular positions in relation to a circumferential direction thereof (for example, refer to Patent Literature 1).
One of the plurality of light blocking plates is brought on to an optical path which connects a light source with a projection lens as a result of the rotary shade being rotated around the turning axis. This blocks part of light which is emitted from the light source, and the edge shape of the light blocking plate is projected to the front of the vehicle through the projection lens. Then, a circumferential edge portion of a light distribution pattern which is formed ahead of the vehicle has a shape which corresponds to the edge shape of the light blocking plate. A plurality of light distribution patterns can be formed selectively by selecting the light blocking plate to be disposed on the optical path although the lamp unit uses the single light source.
As the plurality of light distribution patterns, there are known a low beam pattern which illuminates a near field ahead of the vehicle so as not to dazzle a preceding vehicle and a high beam pattern which illuminates a field expanding far ahead of the vehicle. Further, there is known a light distribution pattern in which only an area where a vehicle or a pedestrian is detected to be present ahead of the vehicle is not illuminated to be kept as a non-illuminated area in such a state that high beams are shined so that the forward visibility is ensured while restricting the dazzling of the vehicle or the pedestrian present ahead of the vehicle. In this description, this light distribution pattern will be called a “partial high beam pattern.”
As described in Patent Document 1, in a left headlamp, a partial left high beam pattern is formed in which a top right-hand side portion is made into a non-illuminated area, and in a right headlamp, a partial right high beam pattern is formed in which a top left-hand side portion is made into a non-illuminated area. Then, a partial high beam pattern like the one described above can be formed by superposing those partial high beam patterns one on the other. The position and size of the non-illuminated area can be changed by executing a swivel control to swivel an optical axis of the lamp unit in the left-to-right direction.
A rotary shade is known which includes a twisted end face which extends around a turning axis so as to connect different positions in relation to the direction of the turning axis (refer to Patent Document 2, for example). The twisted end face is a portion which is projected as a boundary of a non-illuminated area which is formed partially in a high beam pattern. Since a position of the twisted end face to be projected changes in relation to the direction of the turning axis as the rotary shade turns, the position of the boundary of the non-illuminated area, that is, the position and size of the non-illuminated area can be changed without executing the swivel control.